Project Summary/Abstract Globoid cell leukodystrophy (GLD), commonly referred to as Krabbe disease, is a debilitating and always fatal pediatric neurodegenerative disease caused by a mutation in the gene encoding for the hydrolytic lysosomal enzyme galactosylceramidase (GALC). Accumulation of cytotoxic psychosine, a target of GALC, results in loss of oligodendrocytes and Schwann cells and widespread central and peripheral nervous system demyelination. Neurologic dysfunction is apparent in the first year of life and death often occurs by two years of age. Notably, GLD is a naturally occurring hereditary disease in dogs for which a breeding colony was established; Dr. Bradbury and her mentors currently maintain this breeding colony. Disease progression in GLD dogs closely recapitulates clinical, pathological, and biochemical abnormalities of human disease. The predictable disease progression and lifespan (15.7 4.8 weeks of age) allow for timely identification of pathological changes and evaluation of therapeutic interventions. Furthermore, the increased size and complexity of the canine brain are similar to that of an infant allowing for implementation of clinically relevant methods to evaluate disease progression and therapeutic strategies. The long-term goal is to conduct therapy trials in this valuable large animal model to inform pediatric clinical trials. However, preliminary adeno-associated virus (AAV) studies in the GLD dog have provided insights to critical limitations of current gene therapy protocols. The applicant believes that it is vital to further elucidate underlying pathogenic mechanisms hindering therapy in this particular model and subsequently consider more novel gene therapy approaches to treat this disease. Herein Dr. Bradbury will use the canine model of GLD to further define the neurotoxic effect of psychosine on canine oligodendrocytes and use these data to develop temporospatial targeting of GALC delivered via AAV vectors to treat disease in this naturally occurring animal model. In the K99 phase she will evaluate the effect of psychosine on canine oligodendrocyte maturation and how this impacts rescue by gene therapy. She will also determine the temporospatial accumulation of psychosine in the brain and spinal cord and how it relates to the timing of myelin maturation in the canine brain. In the R00 phase Dr. Bradbury will focus on developing strategies to improve GALC biodistribution and targeting of pyschosine. Advances in AAV biology over the past decade provide for more tailored therapeutic approaches by targeting specific tissues, cells, and receptors. The K99/R00 funding mechanism will provide a necessary transition from NRSA postdoctoral fellow to an independent investigator. In addition to gaining new laboratory skills, the applicant's career development will be enhanced by the expertise of an exceptional advisory/mentoring committee. Additionally, the University of Pennsylvania is a top tier research institution with unparalleled resources and ample educational and training opportunities. The outstanding mentoring, unmatched resources, and strong commitment from her department will strengthen Dr. Bradbury's candidacy for, and transition to, an independent tenure-track faculty position. !